On Wednesday, September 07, 2011 07:52:38 pm Niken Wijaya wrote:
I think I have to clarify that I used MBACK to do the normalization instead of ATHENA. This might as well explain why I got such a high value of y-axis offset, why you think I did not choose the right parameters for the "pre-edge" and "normalization range" and also why I imported the data as normalized mu(E) rather than mu(E). As mentioned in the manual, doing normalization in Athena is very subjective, tiny difference in the point chosen for both the "pre-edge region" and "normalization range" will result in different normalized spectra. Due to lack of experience in processing XAFS spectra and noisy spectra obtained, I was planning to eliminate this problem by using MBACK. My initial plan was to combine the benefit I can get from both ATHENA and MBACK. So, I did the normalization using MBACK, then do the self-absorption correction and fit the normalized spectra in ATHENA. However, looking at your comment, LCF in ATHENA requires edge-step normalization, by saying that, does it mean that I cannot normalized my spectra using MBACK then fit them in ATHENA?
Niken, So, you want to use MBACK because it is less subjective than Autobk. How, then, do you then plan to do your self absorption correction in a similarly and defensibly rigorous manner? I am suspicious that you have not thought this through very well. Your original email suggested that you believed there to be a problem with Athena. A cursory examination of your work -- once you actually did the favor of posting a project file -- made it clear to me that you are not using the program correctly. Indeed, in one of your emails, you made it clear that you have never read the documentation. I am unaware of a bug in Athena that precludes using data normalized outside of Athena to do LCF within Athena. That may not be the mornal mode of operation, but it is a reasonable thing to want to do. You must take care to import the data correctly and verify that the form of your data has been preserved before performing the LCF. If you expect the program to magically do what you want rather then observing how the program actually behaves, it is unlikely that you will be satisfied with the results. Is it possible that there is a bug that precludes Athena from doing this thing? Of course. A quick examination of the archives of this mailing list should make it clear that my software is *way* less than perfect. So far, you have not given me any reason to belive that's the case. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 My homepage: http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/ifeffit/Demeter